How to deal with dangerous neighbor?

ok so for about a few yrs now, this neighbor of ours keeps saying that my dad goes into his house, eats his food and yet when he comes home nothing is out of place. he says my dad trows dead skunks in property, underwear and rocks. He has added pointy metal sticks to our existing shared fence. He even lays down wood with nails pointing up, so if anyone jumps the fence they will get hurt. He installed cameras pointing to our house, and even put up a "private property" sigh facing our house. It has come to the point that my dad was walking out of a hardware store a block from our house and the guy was waiting for him outside to fight. other neighbors too have had problems with this guy. He believes everyone is after him, and hates that he has no proof to show. He even tried paying another neighbor 50 bucks to get a picture of my dad inside his house, because his cameras haven't caught him. what do we do? do we call the police? there is something wrong with this guy and needs help. He is always trying to fight my dad when he sees him, and he has said somethings to my brother also. this is getting outta hand, and we need to stop it before someone gets hurt.